<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>

    <style>
      .onepx-border {
  margin-top: 10px;
  width: 200px;
  height: 80px;
  cursor: pointer;
  line-height: 80px;
  text-align: center;
  font-weight: bold;
  font-size: 50px;
  color: #f66;
}

.onepx-border:first-child {
  margin-top: 0;
}

.normal {
  border: 1px solid #f66;
}

.thin {
  position: relative;
}

.thin::after {
  position: absolute;
  left: 0;
  top: 0;
  border: 1px solid #f66;
  width: 200%;
  height: 200%;
  content: "";
  transform: scale(0.5);
  transform-origin: left top;
}

    </style>
  </head>
  <body>
    <div class="bruce flex-ct-y">
      <div class="onepx-border normal">1px</div>
      <div class="onepx-border thin">0.5px</div>
    </div>
  </body>
</html>
